Liner/casing buoyancy arrangement, method and system

ABSTRACT

An arrangement for a buoyant liner or casing string including a shoe plug affixed to the string and configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string.

BACKGROUND

In the resource recovery industry liners and casings are often disposed in boreholes as part of a completion operation. When a borehole is vertical this is relatively easy in that the casing is urged by gravity to penetrate the borehole. When boreholes are highly deviated of horizontal however, running a casing therein becomes more difficult since the same gravitational force that helped in the vertical section will cause the casing to drag against the low side wall of the borehole making friction a complicating factor for running the casing string. To alleviate the issue, the art has used plugs in the casing string to trap air therein thereby taking advantage of the buoyancy effect of the less dense air relative to the denser mud and “floating” the casing. This reduces the problem in the first instance but then creates its own problems since the plugs must somehow be removed. Various methods have been tried but the art is always receptive to more efficient arrangements.

SUMMARY

An embodiment of an arrangement for a buoyant liner or casing string including a shoe plug affixed to the string and configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string.

An embodiment of a borehole system including a borehole in a subsurface formation, a string in the borehole, a shoe plug affixed to an end of the string the shoe plug configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string.

A method for managing a borehole including affixing a shoe plug to a string, the shoe plug configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string, running the string to depth, applying pressure to the inside of the spring to exceed pressure outside of the string, and unseating the shoe plug to allow full bore flow in the string.

An embodiment of a casing/liner string buoyancy arrangement including 3 or more seals in the string spaced apart from one another, a chamber defined between each two adjacent seals instituting a plurality of chambers, the plurality of chambers and contents therewithin having a lower specific gravity than borehole fluid anticipated to be encountered by the arrangement, during use.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a schematic view of a borehole system with a casing and plug therein in accordance with this disclosure;

FIG. 2 is a float shoe plug configured in accordance with this disclosure; and

FIG. 3 is a plug configured in accordance with this disclosure; and

FIG. 4 is a schematic view similar to FIG. 1 but illustrating a plurality of chambers.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring to FIG. 1 , an arrangement 10 includes a casing or liner string 12 illustrated disposed within a borehole 14 in a subsurface formation 16. The string 12 includes a float shoe plug 18. The string 12 may also include a plug 20 in some embodiments. The above noted components and their more detailed descriptions below constitute both an arrangement 10 as claimed and a system 40 as claimed. A method for managing a borehole is also disclosed.

Referring to FIG. 2 , the float shoe plug 18 is disclosed in greater detail. Float shoe plug 18 effects a fluid seal. The shoe plug 18 is configured to resist a significant differential pressure thereacross in one direction while being responsive to a small differential pressure acting in an opposite direction across the shoe plug 18 to unseal. This is helpful in that the shoe plug 18 is well capable of holding the differential between downhole pressure and an atmospheric volume on the other side of the shoe plug 18 for excellent buoyancy creation while still being very easily disabled for full bore flow. As will be appreciated from FIG. 1 , the shoe plug 18 is at or near a downhole end 22 of the string 12. The shoe plug 18 in this position resists hydrostatic pressure in the borehole 14 at depth while atmospheric pressure (or other lower pressure) is inside of the string 12. It is noted that for this embodiment the plug 20 is not used and the entire string 12 is at substantially less than hydrostatic pressure due to being open to surface atmosphere at an uphole end thereof. The shoe plug 18 is configured to robustly resist the differential pressure thereacross in this direction and will prevent borehole fluids entering the string 12 from the downhole end 22 thereof. The shoe plug 18 in an embodiment is configured in a two-piece format with a cone 24 and a seat 26. Configured as shown in FIGS. 1 and 2 , the cone 24 is energized into its seat 26 by the higher hydrostatic pressure surrounding the end 22 versus the atmospheric pressure within the string 12. In this condition, the atmospheric pressure in the string 12 tends to increase buoyancy of the string 12 and thereby reduces gravity-based friction on the string 12 while running. Advantageously, due to the construction of the shoe plug 18, while it is capable of holding substantial pressure differential toward the inside of string 12, it takes very little applied pressure inside of the string 12 to unset the cone 24 from the seat 26 and allow fluid to move around the shoe plug 18. This is due to the conical or frustoconical shape, or spherical shape or other plug shape of the cone 24 that seats in a sealing manner against the seat 26 but is not substantially retained in the opposite direction. In an additional advantage, the shoe plug 18 may comprise a readily degradable material that will dissolve in a few days, if desired, or the shoe 18 may simply be left at the toe of the borehole 14. Such degradable materials are to be understood to be degradable within a number of hours to a number of days. Degradable material should not be construed to mean any material that experiences corrosion since degradable materials are intended to be vanquished in relatively short order whereas other materials that are actually intended to survive for long periods of time may still be technically corrodible. It is not the intent of this disclosure to be construed to cover such corrodible material as regular steel, which is of course intended to be durable for many years. The materials contemplated herein include controlled electrolytic material or disappear on demand material available from Baker Hughes, Houston Tex., or may be some other mechanically sufficient material that will degrade and substantially disappear in a few hours to a few days from a trigger (electrical trigger, fluid pill trigger, exposure to ambient fluid trigger, etc.)

In another embodiment, the plug 20 may also be employed. Plug 20 is a seal member and functions to segregate a portion of the string 12 between plug 20 and shoe plug 18 as a captured atmospheric (or other pressure lower than ambient downhole pressure, or a liquid having a lighter weight than the drilling mud) chamber 28. Hence pressure within the chamber 28 is maintained at all times. This allows operating parameters such as filling a vertical portion 30 of the string 12 with a liquid thereby increasing its weight. The load created by the liquid in the vertical section of the string 12 is useful to help push the string 12 into a highly deviated or horizontal portion of the borehole 14, especially when employing the buoyancy that the atmospheric chamber 28 presents. In an embodiment, the plug 20 is configured as illustrated in FIG. 3 . The embodiment includes a trigger 32 for a disappear on demand material 34 (such material being available from Baker Hughes, Houston, Tex.). The trigger 32 may be an igniter in some cases. In any event, the plug 20 is triggerable at will and will rapidly (e.g., in a matter of hours) degrade and disappear. This allows for the application of pressure from surface to reach the shoe plug 18 which pressure will have the effect disclosed above to unseat the cone 24 and open the shoe plug 18 to regain full bore flow capability in string 12.

Accordingly, embodiments of the arrangement 10 facilitate rapid and reduced friction deployment of casings and liners into boreholes having a deviation of horizontal section. Then the shoe plug 18 and optionally plug 20 are easily disposed of leaving a full bore in the casing or liner string 12.

A method for managing a borehole includes affixing a shoe plug 18 to a string 12. Running the string to depth and applying pressure within the string to unseat the cone 24 in the seat 26 of the shoe plug 18. An alternate method includes the above but also before running, affixing a plug 20 to the string, running to depth, triggering the plug 20 to disappear and pressuring up on the string to unseat the cone 24 in the seat 26 of the shoe plug 18.

In another embodiment, referring to FIG. 4 , a plurality of plugs 20 are employed to create a plurality of chambers 28. In such an embodiment, sequential plugs 20 are individually addressable and may be opened individually to adjust buoyancy in an incremental manner. For example, Plug 20 a may be opened (disappeared, degraded, dissolved, etc.) before plugs 20 b or 20 c and before any changed to the shoe plug 18. This would allow liquid to flow into chamber 28 a but not into chamber 28 b. Buoyancy would be reduced from the level presented when chamber 28 a remained sealed off by plug 20 a but still greater buoyancy than would be the case when all plugs 20 and shoe plug 18 are removed. In other respects, the plug type and makeup is as in the disclosure above.

It is also to be appreciated that one or more plugs 20 and one or more shoe plugs 18 are contemplated in the same embodiment. Multiple shoe plugs 18 may be removed in the same way as that of FIG. 1 , but in a serial manner. The one or more plugs 20 may also be removed in the same manner as noted above.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1: An arrangement for a buoyant liner or casing string including a shoe plug affixed to the string and configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string.

Embodiment 2: The arrangement as in any prior embodiment, wherein the shoe plug comprises a cone and a seat.

Embodiment 3: The arrangement as in any prior embodiment, wherein at least one of the cone and seat comprise a degradable material.

Embodiment 4: The arrangement as in any prior embodiment further including a plug affixed to the string in spaced relationship to the shoe plug to create a pressure chamber of lower pressure than ambient hydrostatic pressure when run in a borehole.

Embodiment 5: The arrangement as in any prior embodiment, wherein the pressure chamber is an atmospheric pressure chamber.

Embodiment 6: The arrangement as in any prior embodiment, wherein the plug comprises a disappear on demand material.

Embodiment 7: The arrangement as in any prior embodiment wherein the plug includes a trigger.

Embodiment 8: The arrangement as in any prior embodiment wherein the trigger is an igniter.

Embodiment 9: A borehole system including a borehole in a subsurface formation, a string in the borehole, a shoe plug affixed to an end of the string, the shoe plug configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string.

Embodiment 10: The borehole system as in any prior embodiment further comprising a plug disposed in the string spaced from the shoe plug to create a pressure chamber.

Embodiment 11: The borehole system as in any prior embodiment, wherein the plug comprises disappear on demand material and a trigger.

Embodiment 12: A method for managing a borehole including affixing a shoe plug to a string, the shoe plug configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string, running the string to depth, applying pressure to the inside of the spring to exceed pressure outside of the string, and unseating the shoe plug to allow full bore flow in the string.

Embodiment 13: The method as in any prior embodiment further including affixing a plug to the string spaced from the shoe plug to create a pressure chamber therebetween.

Embodiment 14: The method as in any prior embodiment further including triggering the plug to disappear.

Embodiment 15: The method as in any prior embodiment further including degrading the shoe plug.

Embodiment 16: A casing/liner string buoyancy arrangement including 3 or more seals in the string spaced apart from one another, a chamber defined between each two adjacent seals instituting a plurality of chambers, the plurality of chambers and contents therewithin having a lower specific gravity than borehole fluid anticipated to be encountered by the arrangement, during use.

Embodiment 17: The arrangement as in any prior embodiment wherein one or more of the seals comprises a degradable material.

Embodiment 18: The arrangement s in any prior embodiment wherein one or more of the seals comprises a disappear-on-demand material.

Embodiment 19: The arrangement s in any prior embodiment wherein at least one of the plurality of chambers contains a gas or fluid.

Embodiment 20: The arrangement s in any prior embodiment wherein the seals are individually addressable to unseal such that fluid exchange in a specific one or more of the plurality of chambers is enabled.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “about”, “substantially” and “generally” are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” and/or “substantially” and/or “generally” can include a range of ±8% or 5%, or 2% of a given value.

The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a borehole, and/or equipment in the borehole, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. 

1. An arrangement for a buoyant liner or casing string comprising: a shoe plug affixed to the string and configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string.
 2. The arrangement as claimed in claim 1, wherein the shoe plug comprises a cone and a seat.
 3. The arrangement as claimed in claim 2, wherein at least one of the cone and seat comprise a degradable material.
 4. The arrangement as claimed in claim 1 further including a plug affixed to the string in spaced relationship to the shoe plug to create a pressure chamber of lower pressure than ambient hydrostatic pressure when run in a borehole.
 5. The arrangement as claimed in claim 4, wherein the pressure chamber is an atmospheric pressure chamber.
 6. The arrangement as claimed in claim 4, wherein the plug comprises a disappear on demand material.
 7. The arrangement as claimed in claim 6 wherein the plug includes a trigger.
 8. The arrangement as claimed in claim 7 wherein the trigger is an igniter.
 9. A borehole system comprising: a borehole in a subsurface formation; a string in the borehole; a shoe plug affixed to an end of the string, the shoe plug configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string.
 10. The borehole system as claimed in claim 9 further comprising a plug disposed in the string spaced from the shoe plug to create a pressure chamber.
 11. The borehole system as claimed in claim 10, wherein the plug comprises disappear on demand material and a trigger.
 12. A method for managing a borehole comprising: affixing a shoe plug to a string, the shoe plug configured to hold a pressure differential from a higher pressure outside of the string to a lower pressure inside of the string and to unseat upon a pressure differential of a higher pressure inside of the string to a pressure outside of the string; running the string to depth; applying pressure to the inside of the spring to exceed pressure outside of the string; and unseating the shoe plug to allow full bore flow in the string.
 13. The method as claimed in claim 12 further including: affixing a plug to the string spaced from the shoe plug to create a pressure chamber therebetween.
 14. The method as claimed in claim 13 further including triggering the plug to disappear.
 15. The method as claimed in claim 12 further including degrading the shoe plug.
 16. A casing/liner string buoyancy arrangement comprising: 3 or more seals in the string spaced apart from one another; a chamber defined between each two adjacent seals constituting a plurality of chambers, the plurality of chambers and contents therewithin having a lower specific gravity than borehole fluid anticipated to be encountered by the arrangement, during use.
 17. The arrangement as claimed in claim 16 wherein one or more of the seals comprises a degradable material.
 18. The arrangement as claimed in claim 16 wherein one or more of the seals comprises a disappear-on-demand material.
 19. The arrangement as claimed in claim 16 wherein at least one of the plurality of chambers contains a gas or fluid.
 20. The arrangement as claimed in claim 16 wherein the seals are individually addressable to unseal such that fluid exchange in a specific one or more of the plurality of chambers is enabled. 